Cruise control systems are used to control vehicle speed and vehicle acceleration. When the cruise control system is active, a driver-selected speed is maintained without requiring the driver to operate the accelerator pedal. The cruise control system is manually activated and controlled by the driver via a cruise control input device. The cruise control system may be deactivated by the cruise control input device, application of a brake pedal and/or application of clutch pedal in vehicles with a manual transmission.
The cruise control system adjusts throttle area to control the speed of the vehicle. With electronic throttle control (ETC), an ETC module implements an ETC algorithm that adjusts the throttle area based on sensors, driver commands and/or cruise control algorithm commands.
The throttle valve controls the torque and speed of the engine by metering the supply of air to the engine. An engine controller modulates fuel based on an estimated airflow entering the engine. Sensors monitor the air flow to the engine and the amount of oxygen in the exhaust. The engine controller typically adjusts fuel delivery so that the air-to-fuel ratio is substantially equal to a stoichiometric value.
Some internal combustion engines (ICEs) include engine control systems that selectively deactivate cylinders under low load situations. For example, an eight-cylinder engine can be operated using four cylinders to improve fuel economy by reducing pumping losses. This process is generally referred to as displacement on demand (DOD). As used herein, activated mode refers to operation using all of the engine cylinders. Deactivated mode refers to operation using less than all of the cylinders of the engine (one or more cylinders not active). When cruise control is active and the engine is operating with minimal reserve torque in the deactivated mode, the DOD engine may frequently transition between the activated and deactivated modes based on changing road load conditions, which may cause perceptible torque disturbances and reduced fuel economy.